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Symantec Client Firewall Remote Access and Denial of Service Issues

Risk Impact
High

Overview
eEye Digital Security notified Symantec Corporation of four vulnerability issues they discovered in the Symantec Client Firewall products for Windows. By properly exploiting these issues, an attacker could render the targeted system inoperable or execute remote code with kernel-level privileges on the targeted system.

Details
eEye Digital Security notified Symantec of four vulnerabilities they discovered during product testing on versions of Symantec's client firewall application. eEye Digital Security found three instances where remote KERNEL-level access could potentially be gained. Additionally, they reported a denial of service (DoS) issue that requires a system reboot to regain system utilization.

All issues occur within routines in the SYMDNS.SYS component.

The first issue is a stack overflow in the processing of DNS responses caused by improper bounds checking of external input. Successful exploitation of this issue could result in remote code execution on the targeted system with kernel-level privileges.

The second issue is a stack overflow in the processing of NetBIOS Name Service responses that can result in a memory overwrite. If an attacker could successfully create the conditions required to manipulate this vulnerability they could potentially execute arbitrary code with kernel-level privileges.

The third remote execution issue is a potential heap corruption problem caused by improper bounds checking in the processing of NetBIOS Name Service responses. If an attacker were to successfully exploit this condition, they could possibly execute arbitrary code on the targeted system with kernel-level privileges.

The forth issue is a potential DoS condition caused by improper handling of DNS response packets. Maliciously configured DNS responses can cause the targeted system to halt requiring a system reboot to clear the condition and regain system access.

Symantec Response
Symantec confirmed the vulnerabilities exist in the consumer and corporate Symantec Client Firewall applications as well as in Symantec's Norton AntiSpam 2004 application. Symantec product engineers have developed fixes for the issues and released patches for all impacted products through Symantec LiveUpdate and technical support channels.

Clients running consumer versions of the affected products who regularly run a manual Symantec LiveUpdate should already be protected against this issue. However, to be sure they are fully protected, customers should manually run Symantec LiveUpdate to ensure all available updates are installed.

Open any installed Symantec product
Click on LiveUpdate in the toolbar
Run LiveUpdate until Symantec LiveUpdate indicated that all installed Symantec products are up-to-date
Depending on the application, system may require a reboot to effectively update available fixes.
Clients running the corporate versions of Symantec Client Firewall or Symantec Client Security should download and apply patches obtained through their appropriate support channels.

Symantec is not aware of any active attempts against or customer impact from this issue.

CVE
The Common Vulnerabilities and Exposures (CVE) initiative has assigned Candidate names to these issues.

Issues one, two and three are assigned under CVE Candidate Name, CAN-2004-0444.

The fourth issue, the Denial of Service in NetBIOS Name Service is assigned CVE Candidate Name, CAN 2004-0445.

These are candidates for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems.

Credit
Symantec appreciates the cooperation of the eEye Digital Security research team in identifying this issue.